The major hypotheses to be tested is that altered levels and patterns of gene expression are present in the brains of patients with depressive illness as compared to normal controls and can be used to define disturbances of the neuronal circuitry of depressed patients involving the dorsal lateral prefrontal cortex (DLPFC), the anterior cingulate gyrus, and the mediodorsal (MD) thalamic nucleus, the paraventricular nucleus (PVN) of the hypothalamus, the hippocampus, and the raphe nuclei. We hypothesize that by simultaneously assessing the levels and expression patterns of thousands of genes from multiple areas of individual brains, we will be able to define a consistent pattern of brain dysregulation in depressed patients that would be difficult if not impossible to recognize by studying the pattern of expression of single genes in single brain regions. The specific research proposed in this application will define the levels and patterns of expression of 10,000 distinct human genes known to be expressed in the brain. These studies will be carried out using samples of five different brain regions (DLPFC; anterior cingulate gyrus, thalamus; hypothalamus; hippocampus; raphe) from a total of 35 matched brain pairs (70 brains total). Ten matched pairs of male and female brains will come from normal individuals. These samples will be studied initially to assess the degree of variability of brain gene expression between normal individuals. The remaining twenty five matched pairs will consist of depressed and control brains. Ten of these pairs of matched depressed/control brains will be used to define changes in gene expression characteristic of depression. The remaining fifteen pairs of matched depressed/control brains will be used in an effort to replicate the gene expression findings from the first ten depressed/control pairs. Specific research aims include: 1) Use the polymerase chain reaction (PCR) to amplify 10,000 different human DNA fragments (Sequence Tagged Sites), each representing a distinct human gene expressed in the brain. 2) Use an automated system to construct micro arrays of the 10,000 brain STSs on glass slides. 3) Use the micro arrays from Aim 2 in conjunction with tissue samples from normal brains to determine the normal range of messenger RNA (mRNA) level for each of the 10,000 genes. 4) Use the microarrays from Aim 2 in conjunction with tissue samples from matched normal and depressed brains to identify consistent alterations in gene expression specific to depressed patients.